This invention relates in general to magnetic tape cassette transport apparatus, and, more particularly, to a magnetic tape cassette transport/accessor assembly, which is movable in horizontal, vertical and lateral directions by means of a belt drive system, which eliminates the need to mount drive motors on the transport/accessor assembly.
In applications in which a large amount of information is stored on electronic media (such as the storage of digital information on a plurality of magnetic tape cassettes), it is often desirable that each unit of storage (e.g., magnetic tape cassette), be accessed in a minimum amount of time. For example, it is desirable to minimize the time required to change over from one cassette to another cassette used in a magnetic tape record/reproduce device. Where the cassette storage system includes a large number of cassette storage compartments, it is also desirable that the cassette be transported between a storage compartment and a record/reproduce device, in a manner which minimizes damage to the cassette through rough or jerky movements in the cassette transport device. Thus, a smooth, gentle acceleration and deceleration of the cassette transport assembly is desired.
Various arrangements have been proposed to actuate a transport assembly to transport an object between spaced locations in a storage system. The simplest type of arrangement uses manual power for actuation of the transport system. (See: U.S. Pat. No. 4,113,119, issued Sept. 12, 1978, entitled APPARATUS FOR LOADING ARTICLES ONTO VERTICALLY SPACED HORIZONTALLY DISPOSED SHELVES.) Although such an arrangement is relatively inexpensive, it is disadvantageous because it is not readily adaptable for use as an automatic storage system. In order to ameliorate this deficiency in manually operated transport systems, it has been proposed to use motors in order to actuate the transport assembly. Typically, at least one or more of the actuating motors are mounted on the transport assembly itself. (See, for example, U.S. Pat. No. 3,557,977, issued Jan. 26, 1971, entitled LOAD DETECTING DEVICE FOR WAREHOUSING SYSTEM, and U.S. Pat. No. 4,614,474, issued Sept. 30, 1986, entitled DEVICE FOR EXCHANGING DISKS.) However, drive motors and drive motor supports, add considerable weight to the transport assembly, thus increasing the stresses on the transport assembly drive and on the transport assembly load-bearing components. Moreover, reliability is reduced and maintenance is made more difficult.
It has been proposed to use a belt or cable system to eliminate mounting one or more motors on moving components of the transport assembly. Thus, for example, in U.S. Pat. No. 4,507,044, issued Mar. 26, 1985, entitled ROBOT AND CONTROL SYSTEM, and U.S. Pat. No. 4,566,346, issued Jan. 28, 1986, entitled AUTOMATED TOOL MANIPULATING STRUCTURE WITH X-Y MOVEMENT INCLUDING A BELT AND PULLEY DRIVE ARRANGEMENT, there are disclosed arrangements in which x and y direction drive motors are not mounted on the member which is moved in the x and y directions. Although these arrangements may be suitable for the purposes for which they were intended, they do not solve the problem of actuating a transport assembly which is movable in three mutually orthogonal directions. Thus, in the latter patent, the x-y drive motors are mounted on a rotating table which is driven by a third motor which is fixedly mounted. Thus, the rotating table is weighted down by the x-y drive motors and motor mounts, requiring a heavier duty bearing to support the rotating table and a larger motor to drive it.